Agricultural feed mixers, often termed Total Mixed Ration (TMR) Mixers, have a goal of providing a homogenous mixture of ingredients that constitute a ration to be fed to livestock for maximum production, whether that production is milk or meat.
There are known methods of controlling the transmission of power from the main power source, usually a tractor engine, connected to the mixing element(s) of a livestock feed mixer by means of a power take-off (PTO) output (e.g., a shaft, belt, etc.). Traditionally this had been done by using a direct drive connection from the tractor engine, through the PTO, to the mixing elements. Variation in the speed of the mixing elements in a direct drive arrangement is achieved by varying the speed of the engine of the tractor. The advent of larger systems and the attendant increase in power demand brought about the use of multi-speed gearboxes having at least two speed ranges or ratios, where a first speed produces a lower output speed than a second speed, but requires less power. One known method of selecting or shifting between the first speed and the second speed is by manual actuation of a shift lever. This method forces the operator to stop the PTO, manually shift the lever to change gears, and then engage the PTO again with the transmission in the different gear, to resume mixing at a different speed. This method wastes time for the operator and reduces the efficiency of the mixing process. This solution also relies on the operator to decide to shift the gearbox at an appropriate time, so as to avoid damage to the drive system components (tractor, engine, drivelines, multi-speed gearbox, mixing element gearbox/reducers), by exceeding their designed loading limits. For an operator, some of the primary indications of the magnitude of loading on these components are visual cues of how full the mixing chamber is, the weight inside the mixing chamber if equipped with a scale system, and possibly an audible cue of the strain on the main power source, such as the tractor engine.